Interpretive Summary: Agriculture is influenced by a multitude of factors, both internal and external to the production system. These influences act to alter the management and production decisions of farmers, often with unexpected consequences. Increasing emphasis has been placed on reducing negative environmental impacts of agricultural production. However, few studies have examined the role of internal and external factors on the net environmental outcomes of production decisions. Nutrients, particularly nitrogen, play a critical role in agricultural production. Nitrogen is needed to boost crop yield, and is produced in livestock systems. Management of nitrogen within the agricultural system is critically important to ensure good production without contamination of the environment. Nutrient balances and budgets are used as tools by national and international organizations to track nutrient loads from agriculture to the environment. The scientists from USDA-ARS and Poznan University, Poland, have examined agricultural production in Mississippi, U.S. and Poland to explore how drivers impact management choices, and how those choices alter the environmental impact of agriculture. Changes in which crops are produced are shown to increase or decrease the gross nitrogen balance. Greater productivity enhances the nutrient balance through better conversion of nitrogen to harvested crop matter. Conversely, confinement animal production contributes large quantities of nitrogenous compounds that must be dealt with within the system. New technologies and management practices must be developed with an emphasis towards sustainable management principles.

Technical Abstract:
Economics is a principle driver impacting management decisions in agricultural production systems. While increasing concern has focused on preserving the natural resource base to ensure continued support for future production, little emphasis has been placed on examining how drivers alter management choices and the subsequent impact on the environment. Efficient nutrient use is critical to ensure economical food production while minimizing the impacts of excessive nutrient applications on the environment. Increasing concerns for future sustainability of agricultural production have led to development of nutrient budgets as indicators and policy instruments for nutrient management. Nitrogen (N) is a key component of agricultural production, both as an input to support crop production and as a waste product of livestock production. Nutrient budgets for N have been developed by the Organization for Economic Cooperation and Development (OECD) as agri-environmental indicators to compare member states and are also used by the USDA-NRCS to develop nutrient management plans. Here, we examine crop and animal production systems, drivers impacting management choices, and the impact of those choices on gross annual N balance as a means of assessing the environmental impacts of agricultural production systems. We use as case studies two very different agronomic production systems in Mississippi, USA and Poland. State and country level data from US Department of Agriculture and OECD databases are used to develop the data set from 1998 to 2008. Changes in cropping systems in response to economic drivers are shown to improve N balance. However, these improvements can be masked by detrimental growing conditions that are outside of the producers’ control. Confinement livestock production contributes excessive N levels to the system that overwhelm the nutrient balance. Use of large area-scale indices such as country or state-wide balances may mask the severity of nutrient imbalances when production systems are regionalized.